25 Years Ago In TIME

American Legion conventioneers in Philadelphia were dying of a mysterious illness. Eventually, DISEASE DETECTIVES would discover the cause to be a bacterium spread through air-conditioning systems, but until then, near panic took hold:

There was an invisible, impersonal mass killer on the loose. The knowledge rekindled, despite all the advances of modern medicine, humanity's ancient memories of epidemics beyond understanding or control. Even as the first waves of shock and fear began to spread, the search for the killer began in one of the most intensive efforts at medical sleuthing ever undertaken in the U.S. Now that the alert had...